ref: 1ed7430691158c6a2a0c5a7bae36e9e49a43a0e2 dir: /lib/std/swap.myr/
pkg std = generic swap : (a : @a#, b : @a# -> void) ;; generic swap = {a : @a#, b : @a# var t t = a# a# = b# b# = t }